In a distributed application or service architecture, application data is commonly maintained for access by multiple users, thereby permitting multiple users to access and operate on the same set of application data. To prevent concurrent operations on the application data, some applications or services maintain an application data state with the application data in a backend system, such as a server. Application data retrieved by a read service for use by another service is always expected to be current. After the data has been operated on, the server must ascertain whether the data operation was performed on current or outdated data by a calling application. One way a server may preserve data in its current state is to employ a lock on the application data stored in the server and being accessed by a user, thereby preventing concurrent changes to the same set of application data. However, holding a lock on a set of application data is only permissible if an application data state is permitted to persist with the stored application data in the backend system. Web services, however, generally are stateless, such that a web service call does not leave any trace in the backend system, other than any changes made to data stored in the backend system. Further, a web service application may not reside on the backend system, but rather, for example, may be offered in an applet in a browser.
Another way a server may determine whether data stored in the database is still current after being operated on is to employ a hash calculation to calculate an identifier for a certain state of the application data. However, given that application data may exist in a multitude of formats, no uniform hash calculation exists to generate an identifier for the various types of application data. Further, in the event a user customizes application data to include various industry- or customer-specific data, the hash calculation does not take into account the customized extension. As a result, any update made to data stored in a backend system which incorporates industry- or customer-specific extensions may not be reflected in the identifier.
Therefore, it would be desirable to have a method and system for determining whether current data retrieved by a web services application remains current after it has been operated on.